Incubator temps dropped overnight

My DD's preschool is trying to hatch some eggs. The eggs have been in the incubator for roughly 7 days. Their regular teacher was out with a sick family member most of yesterday. When she returned this morning she found that someone had adjusted the thermostat yesterday and the temp was down to 86. They could have been this way as long as 18 hrs. Would the eggs still be good? She has candled and some of the eggs are showing signs of development, but she's unsure if the drop in temp for that long hurt them. Any idea if they are still viable without just waiting to see? She wants them to hatch before they get out for the summer so if she needs to start over she would need to do it now rather than waiting full term on these if they are no longer any good. Thanks!

Most of us that have hatched for years at some point in time have had the incubator temps be low. Either by an unplugged cord, mal-function or the electricity going off for hours or a day. I say they will hatch maybe a day or two later but she will have a hatch.